1. Filed of the Invention
The present invention relates to an apparatus for controlling a soap concentration in cleaning solvent used in a dry cleaning machine.
2. Description of the Prior Art
An example of a measuring method of soap concentration of solvents has been disclosed in Japanese Patent Publication No. 21397/1977. According to this method, a surfactant as soap is charged to a dry cleaning solvent, an antistatic preventive agent is mixed therein, and an electrostatic charge quantity on clothing is measured with an electroscope after cleaning and drying of the clothing. Then, the soap concentration is measured on the basis of the opening angle between the leaves of the electroscope.
However, it is difficult to detect the concentration during the cleaning operation with this method. Accordingly, it has been proposed, in a dry cleaning machine using 1,1,1-trichloroethane as the solvent, to dispose a soap concentration detector in a solvent flow channel, thereby to detect the concentration each time (see Japanese Patent Laid-Open No. 98553/1988). In this method, a high frequency alternating voltage is applied to a pair of electrodes disposed in the solvent and fluctuation of a resistance between the electrodes according to the soap concentration is detected
Further, the outline of a control method for soap concentration of cleaning solvent using the latter soap concentration detecting method has been introduced in "WHITE LIFE" No. 43 (issued by Sanyo Electric Tokki Co., Ltd. in October, 1987), page 10 and page 11.